There has been a continued and growing demand for temporary shelters which, until recently, had been addressed with the use of tents. For example, disaster relief and military operations have often required placement of a temporary structure in one location for months or even years. Comparatively, the time and effort required to erect a tent for these applications has not been a major concern.
Temporary shelters of the foldable, collapsible type are generally regarded as being more robust than tents. Such structures utilize accordion-like panels made, for example, of board material having a corrugated inner layer covered with a smooth facing. The facings and the corrugated interior can be made with a durable and water repelling material such as polypropylene. These structures can be shipped in a collapsed format of minimum volume, wherein accordion-like pleats are compressed, and then expanded on location into what is commonly referred to as a tunnel structure. Typically, a flattened sheet of the board material is expanded along fold lines to provide a pair of opposing side walls and a roof section of variable length. When formed as an integral component of the collapsed shelter, an attached floor section simultaneously expands with the walls and roof section so that a tube-like formation results. In addition, it has been common to add panels to the otherwise open ends of the tunnel to form a closed structure. These end panels may be formed of a fabric, including zippered door openings and the like, or may be formed of rigid material capable of supporting a swing door.
Numerous improvements have been made in the designs of foldable, collapsible shelters, allowing the portable structure to be expanded into an erect, self-supporting structure in less than thirty minutes without a need for special tools. See, for example, U.S. Pat. No. 6,601,598. Still, in many instances, the effectiveness of services, especially emergency operations, can be improved by further reducing set-up times and the number of persons needed to configure the shelters.
In order to facilitate widespread availability and use of portable structures it has been important to improve the performance without affecting cost, weight and portability. In fact, commercial success of relatively inexpensive designs has given rise to new markets which present performance requirements different from those most relevant to long-term applications seen in disaster relief activities. Specifically, there is a growing demand for short term uses with frequent re-deployment of the shelters. Examples include emergency command posts, event first aid stations, mobile hospitals, portable showers for decontamination activities, transitory vending activities and special events.
These more recent product applications often require repetitive opening and closing of the foldable, collapsible shelter on a daily or weekly basis. However, inherent stresses are evidenced by bowing of sheet material after shelters are collapsed into a flattened configuration. With these and other stresses, frequent cyclic movements among folds has affected the durability of the shelter products undergoing frequent cycles of use. By way of example repetitive opening and closing has modified pleat fold vertices from alignment with score lines, resulting in roof failures; and portions of panel material adjacent pattern cuts have been vulnerable to tearing. Generally, portable shelter durability is impacted by repetitive set-up and collapse. Consequently, the structures are prone to ripping along fold lines when being expanded for use. If being deployed in an emergency or time critical situation, such damage may impact a mission by requiring costly time for temporary repair or replacement with another shelter.
The sizes of collapsible foldable shelters have been limited by structural constraints. It has been commonplace to couple shelters of a standard size, e.g., nominally 10 feet wide and 5.5 feet long, into longer lengths (e.g., into a shelter 10 feet wide by a length which is a multiple of 5.5 feet) by slitting an end panel on one shelter and lapping it along an end panel of another shelter. The lapped arrangement can be secured with rivets or other fasteners. However, efforts to assemble structures greater than about 18 feet in length routinely resulted in roof collapse after the shelter was placed in an expanded configuration. Recognizing that customers can receive greater value when larger shelters are provided, it has been a continual desire to counter or overcome the mechanisms which have led to roof collapse. For example, long shelters have been produced with structural roof reinforcement. However, these systems have had visibly noticeable out-of-vertical end walls, requiring extra support such as propping end walls up into plumb positions with the assistance of poles.
With an increasing demand for using portable structures in short-term activities, it is desirable to provide units which are lighter in weight, more portable, easier to deploy and repack, and capable of enduring many cycles of use. When placed in demanding situations such structures should be most capable of withstanding exposure to a variety of harsh physical and chemical environments. While the design of a temporary structure can be optimized for a specific application, it is also desirable to provide a single product suitable for the widest variety of applications. Users could then realize economy through volume purchase and potential inventory reduction, being able to deploy the same structure for different functions and in differing environments. In applications such as disaster relief, it may be necessary to transport large inventories on short notice to quickly respond to short term demands. It would therefore be optimal to have a very compact and light-weight design which meets multiple use requirements. In addition to reducing inventory and transportation costs, these enhanced attributes can improve emergency response times.
As design improvements are sought, the solutions leading to higher performance should not involve trade-offs between individual performance features. For example, creating portable structures which are lighter in weight should not be at the expense of incorporating lower density materials that compromise the performance and durability of the shelter. Otherwise the shelter may experience failure due to stress, strain or abrasion experienced during repeated cycles of set-up, use and re-packing. Nor should the ease and speed of assembly require greater cost. Designs are needed which render shelters more resilient, less susceptible to roof deformations and more capable of supporting the weight of accessory items such as shower systems.
Generally there is a need for improving numerous performance parameters for portable shelters, including durability, speed of deployment and re-packing, windloading, packing density and attainable size. It is desirable to provide designs which are stronger, easier to transport, and more space efficient when compacted—all without compromising durability, comfort or convenience.
Unless otherwise indicated, like reference numbers are used to denote like or similar features among the figures, including the various embodiments.